In Institute of Electrical and Electronics Engineers (IEEE), Wireless Local Area Network (WLAN) is standardized in the IEEE 802.11 specifications, e.g. in IEEE Standard for Information technology—Tele-communications and information exchange between systems, Local and metropolitan area networks—Specific requirements, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. WLAN is a technology that mainly operates in the 2.4 GHz or 5 GHz band. The IEEE 802.11 specifications regulate the physical layer between access points and wireless terminals, MAC layer and other aspects to secure compatibility and interoperability between access points and portable terminals, referred to as STA herein. WLAN is generally operated in unlicensed bands, and as such, communication over WLAN may be subject to interference sources from any number of known and unknown devices. WLAN is commonly used as wireless extensions to fixed broadband access, e.g. in domestic environments and hotspots like airports, train stations and restaurants and the like.
Recently, WLAN has been subject to increased interest from cellular network operators, not only as an extension to fixed broadband access. Instead, the interest is mainly focused on using the WLAN technology as an extension, or alternative to, cellular radio access network technologies. By use of WLAN technology as an extension to cellular radio access network technologies it is contemplated that an ever increasing wireless bandwidth demand may be handled. Cellular operators that currently serve mobile users with, e.g. any of the Third Generation Partnership Project (3GPP) technologies, Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code Division Multiple Access (WCDMA), or Global System for Mobile communications (GSM), treat WLAN as a technology that may provide good support in their regular cellular networks. The term “operator-controlled WLAN” refers to a WLAN deployment that on some level is integrated with a cellular network operator's existing network and where the 3GPP radio access networks and the WLAN wireless access may even be connected to the same core network and provide the same services.
Currently, there is intense activity in the area of operator-controlled WLAN in several standardization organizations. In 3GPP, activities to connect WLAN access points to the 3GPP-specified core network are pursued. Furthermore, in the Wi-Fi Alliance (WFA), activities related to certification of WLAN products are undertaken. The certification of WLAN products is to some extent also driven by the need to make WLAN a viable wireless technology for cellular operators seeking to support high bandwidths in their networks. The term WLAN offload is commonly used and points towards that cellular network operators seek means to offload traffic from their cellular networks to WLAN, e.g. in peak-traffic-hours and in situations when the cellular network for one reason or another needs to be off-loaded, e.g. to provide requested quality of service, maximize bandwidth or simply for coverage. Furthermore, the operators are also seeking effective ways for moving terminals from the WLAN back to the 3GPP networks, e.g. if the network conditions have changed. Such activities are currently being promoted in the WFA.
A wireless operator, offering a mix of two technologies that are standardized in isolation from each other, i.e. the WLAN technologies and the cellular technologies, is thus faced with a challenge of providing intelligent mechanisms for co-existence of these technologies within one system that is controlled and operated by the wireless operator. As mentioned above, up until now, 3GPP and WLAN have evolved as two separate systems, being standardized up to a great extend in isolation from each other. However, recent activities in 3GPP and WFA have taken initiatives to improve the interoperability between the WLAN and cellular technologies. Increased interoperability is intended to provide mobile operators, or wireless operators, with greater control over their “operator-controlled” WLANs.
These recent activities have for example dealt with how to steer portable terminals from WLAN to cellular network.
In WFA, there have been activities that look into the problem of moving terminals from WLAN to the cellular network. A couple of use-cases have been proposed.
An “at-association” use case is proposed. This use-case describes the scenario where a STA, during the connection procedure to WLAN, is moved to the cellular network due to, e.g. high load in the WLAN, unsatisfactory local interference environment, etc.
A “post-association” use-case is proposed. This use-case describes the scenario where a STA, after having been connected to WLAN for a certain amount of time, is moved to the cellular network.
“At-Association” Use-Case
A multi-mode STA, having both, at least one Wi-Fi radio and at least one cellular radio technology, attempts to associate to an Access Point (AP). The AP may have knowledge of its current load, the interference situation, U/L signal strength at the AP and AP network connection status. Because of one or more of these parameters, the AP refrains from accepting additional STAs to its network.
To solve the problem, the AP should be able to explicitly steer or direct the multi-mode STA to a network that could provide a better service—in this case a cellular one. In this way, the Wi-Fi load is not further aggravated and the user experience is maintained or improved.
The AP and the cellular base station may be co-located, e.g. in an integrated picocell, or may be separate Wi-Fi APs “under”, i.e. controlled by, a macro cellular basestation.
The cellular and Wi-Fi networks may be authenticated by the same operator. Both networks are typically, but not necessarily, deployed by the same operator who strives to offload or maximize user experience.
“Post-Association” Use-Case
A multi-mode STA, having both Wi-Fi radio(s) and cellular radio(s), is associated to an AP. The AP has knowledge of its current load, the interference situation, U/L signal strength at the AP and AP network connection status. At a certain point in time, one or more of these parameters reach an unacceptable level.
To solve the problem, the AP should be able to explicitly steer or direct the multi-mode STA to a network that could provide a better service—in this case a cellular one. In that way, the Wi-Fi load is alleviated and the user experience is maintained or improved.
The AP and the cellular basestation may be co-located, e.g. in an integrated picocell, or may be separate Wi-Fi APs “under” a macro cellular basestation.
The cellular and Wi-Fi networks may be authenticated by the same operator. Both networks are typically, but not necessarily, deployed by the same operator looking to offload or maximize user experience.
In both use-cases described above, a problem is related to how the AP shall obtain knowledge about that the particular STA that it attempts to steer to the cellular network has indeed connection to that cellular network.